However, aromatic hydroxylation reactions by the metal-superoxo species are yet to be demonstrated. In this study, we report for the first time that the hydroxylation of aromatic compounds such as anthracene and its derivatives by a mononuclear nonheme Cr(III)-superoxo complex, [(Cl)(TMC)CrIII(O2)]+ (1), occurs in the presence of triflic acid (HOTf) via the rate-determining proton-coupled electron transfer